The present invention relates to novel water-soluble thiourea dioxide derivatives and a process for preparing same.
Thiourea dioxide is in wide use as a reducing agent in the dying industry and the photographic industry because it exhibits a strong reducing ability in a basic aqueous solution.
In the polymer industry and the field of organic chemistry, moreover, studies have been made about using thiourea dioxide as a stabilizer for various compounds (see U.S. Pat. Nos. 2,472,868 and 3,070,569), as a curing agent for amino resins (see German Patent No. 1,215,363 and French Patent No. 1,445,045), or as a polymerization initiator in the polymerization of vinyl monomers using thiourea dioxide together with iron-hydrogen peroxide (see Am. Dyest. Dep. 75, 26-34 (1986). And actually thiourea dioxide has come to be used as such agents gradually.
In the field of polymer industry and that of organic chemical industry, however, the application range thereof is limited because thiourea dioxide is insoluble in almost all organic solvents, and its industrial use in these fields is actually very limited. Although thiourea dioxide dissolves in water, the solubility thereof is 30 g/l or so, which is not always sufficient, depending on the field in which it is used.
Several derivatives of thiourea dioxide have also been proposed with a view to improving the solubility and other properties and expanding the application field. For example, in J. Chem. Soc. Perkin II. 4.1500 (1972) and Synth. Commun. 4.389 (1974) there is proposed a method wherein thiourea derivatives such as N,N'-diphenylthiourea, N,N'-dibenzylthiourea and N,N'-dicyclohexylthiourea are oxidized with hydrogen peroxide to prepare corresponding thiourea dioxide derivatives. However, this method is of little industrial utility because it is difficult to obtain such starting thioureas industrially.
It is the object of the present invention to provide novel thiourea dioxide derivatives superior in water-solubility as compared with thiourea dioxide, having a sufficient reducing ability and capable of being manufactured easily from materials which are easily available industrially.